Neurocognitive impairment after critical illness

More than 5 million individuals are admitted to intensive care units (ICUs) in North America annually. Due to improvements in treatment, increasing numbers of these individuals survive and go on to develop long-term neurocognitive impairment in a variety of cognitive domains. As evidence from over two dozen studies demonstrates, neurocognitive impairment occurs in up to two-thirds of individuals. While it may be particularly common in those with pre-existing vulnerabilities, even patients who are young with robust health prior to critical illness are at risk of post-ICU neurocognitive impairment. While neurocognitive impairment may improve over time and even dissipate in a subset of ICU survivors, neurocognitive impairment is often permanent and, in some cases may be progressive. As commonly occurs in the context of acquired brain injury, the neurocognitive impairment observed after critical illness is typically diffuse, although domains including memory, attention, and executive functioning are often particularly impaired. This impairment is sufficiently severe to negatively impact daily functioning. Although the risk factors and mechanisms undergirding neurocognitive impairment have yet to be fully elucidated, potential contributors include inflammation, hypoxia, and delirium. While one way to impact on the prevalence and incidence of cognitive impairment after critical illness is to attempt to modify key ‘in-hospital’ risk factors, another approach involves the use of post-ICU cognitive rehabilitation, which is increasingly being successfully employed with other impaired medical populations.